ppoints                 package:base                 R Documentation

_O_r_d_i_n_a_t_e_s _f_o_r _P_r_o_b_a_b_i_l_i_t_y _P_l_o_t_t_i_n_g

_D_e_s_c_r_i_p_t_i_o_n:

     Generates the sequence of "probability" points '(1:m - a)/(m +
     (1-a)-a)' where 'm' is either 'n', if 'length(n)==1', or
     'length(n)'.

_U_s_a_g_e:

     ppoints(n, a = ifelse(n <= 10, 3/8, 1/2))

_A_r_g_u_m_e_n_t_s:

       n: either the number of points generate or a vector of
          observations.

       a: the offset fraction to be used; typically in (0,1).

_D_e_t_a_i_l_s:

     If 0 < a < 1, the resulting values are within (0,1) (excluding
     boundaries). In any case, the resulting sequence is symmetric in
     [0,1], i.e., 'p + rev(p) == 1'.

     'ppoints()' is used in 'qqplot' and 'qqnorm' to generate the set
     of probabilities at which to evaluate the inverse distribution.

_R_e_f_e_r_e_n_c_e_s:

     Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) _The New S
     Language_. Wadsworth & Brooks/Cole.

_S_e_e _A_l_s_o:

     'qqplot', 'qqnorm'.

_E_x_a_m_p_l_e_s:

     ppoints(4) # the same as  ppoints(1:4)
     ppoints(10)
     ppoints(10, a=1/2)

